1. Field of the Invention
This invention relates to a process for the transformation of glycerol into 1,3-propanediol on an industrial scale by means of preferably anaerobic microorganisms.
2. Description of the Related Art
In the oleochemical transformation of fatty acid triglycerides into fatty acid derivatives, such as fatty acid methyl esters or fatty alcohols, glycerol is formed from the splitting of the triglycerides.
It is known from the scientific literature that a number of microorganisms, including above all anaerobic microorganisms, are capable of growing on glycerol and of transforming glycerol in the process into other products. One of the metabolites observed in this process is 1,3-propanediol.
1,3-Propanediol is a diol with many applications which, in principle, may be used for the same purposes as ethylene glycol, propylene glycol (1,2-propanediol) or butanediol. Hitherto, 1,3-propanediol has been obtained by addition of water onto acrolein and subsequent hydrogenation. However, the chemical process is so expensive that the end products obtained are unsuitable for many potential applications on account of their high price.
The transformation of glycerol into 1,3-propanediol by microorganisms is mentioned in a few places in the scientific literature. Thus, the metabolism of glycerol by Klebsiella aerogenes NCTC 418 in chemostat cultures is described by H. Streekstra et al in Arch. Microbiol. (1987), 147: 268-275. Although the action of a special Klebsiella aerogenes strain on glycerol in different media is discussed in this Article, there is nothing to help the expert to evaluate the special metabolic performances of such organisms for an industrial process. Applied and
Environmental Microbiology, April 1987, pages 639-643, teaches that Clostridium butyricum NRRL B593 and Clostridium butyricum NRCC 33007 grow with glycerol in batch and Chemostat culture conditions. The same paper also teaches that Clostridium butyricum NRRL B593 and Clostridium butyricum NRCC 33007 grow in a chemically defined medium containing 2% (wt/vol) glycerol as the sole carbon source producing 1,3-propanediol as the major fermentation product. The reference does not teach or suggest that any microorganism disclosed therein will not be catabolically repressed by elevated 1,3-propanediol concentrations.
The problem addressed by the present invention is to provide an industrially workable process for the transformation of glycerol into i,3-propanediol in media having a glycerol content of from about 5% to about 20% by weight by microorganisms which do not suffer catabolic repression by the correspondingly high 1,3-propanediol produced by the process. Additionally, this process is intended to use triglyceride processing streams accumulating in the industrial processing of triglycerides as its starting material.
More particularly, the problem addressed by the invention is to provide a corresponding process which starts out from strains of which the fermentation is easy to handle on an industrial scale and which are capable of converting high concentrations of glycerol into propanediol under standard fermentation conditions with a volume/time yield of more than 0.5 g h.sup.-1. 1.sup.-1 without the expected catabolic repression which is normally encountered with media accumulating such high 1,3-propanediol concentrations. The strains which can be used in the process include Clostridium butyricum SH 1 (DSM 5431) and AK 1 (DSM 5430) and also from Klebsiella pneumoniae strains, such as K. pneumoniae DSM 2026, and also K. oxytoca NRCC 3006.